The disclosure relates to inspection of machinery and, more specifically, inspection using a robot inserted into an annular gap space, such as an air gap, in a generator, electric motor, or turbomachine, including turbo-generators.
The disclosure is related to concurrently filed U.S. patent application Ser. No. 15/652,730, entitled “MODULAR CRAWLER ROBOT FOR IN SITU GAP INSPECTION” filed Jul. 18, 2017, the entire contents of which are incorporated herein by reference. The disclosure is related to concurrently filed U.S. patent application Ser. No. 15/652,771, entitled “END REGION INSPECTION MODULE AND METHOD FOR IN SITU GAP INSPECTION ROBOT SYSTEM” filed Jul. 18, 2017, the entire contents of which are incorporated herein by reference. The disclosure is related to concurrently filed U.S. patent application Ser. No. 15/652,859, entitled “OMNIDIRECTIONAL TRACTION MODULE FOR A ROBOT” filed Jul. 18, 2017, the entire contents of which are incorporated herein by reference. The disclosure is related to concurrently filed U.S. patent application Ser. No. 15/652,680, entitled “IN SITU GAP INSPECTION ROBOT SYSTEM AND METHOD” filed Jul. 18, 2017, the entire contents of which are incorporated herein by reference.
A visual, mechanical, and/or electrical inspection and testing of a generator, electric motor, or turbomachine should be performed on a periodic basis. For example, generators may be inspected and tested periodically in the field for stator wedge tightness, visual surface anomalies, electromagnetic core imperfections, etc. Generator/stator inspection and testing procedures may require complete disassembly of the stator and removal of the generator rotor from the stator before any inspections or tests can be performed on the unit. The cost of disassembly and removal of the rotor, the time it takes for this process, and the dangers of rotor removal may impact the frequency of such inspections.
In situ inspection of generators has been performed employing poles, trolleys, scopes, and rotor turning techniques. These procedures may not accomplish the inspection task in a complete, timely, or safe manner.
Use of a robotic crawler capable of insertion through the radial air gap between the core iron and the retaining ring permits in situ inspection of the rotor and the stator core. The crawler may be inserted in a collapsed position into the gap and expanded by spring return pneumatic rams to the width of the air gap. The crawler may be remotely controlled by a technician and provides video cameras and other inspection tools to perform generator rotor and stator inspections within the air gap as the crawler is driven to selected locations. The crawler may be maneuvered by the technician within the air gap using video for both navigation and visual inspection.
The stator of a typical generator includes a plurality of stator bars. The stator bars are placed in slots, and are held in place in the slots by various components. For example, a resilient member, such as a ripple spring, is placed between a stator bar and a stator wedge in the slot. The stator wedge is retained in the slot at a required preload tightness by the resilient member, to ensure that the stator bar remains securely in place. During in situ maintenance of generators, the amount of preload that the stator wedges are being subjected to requires monitoring. During operation of the generator, the stator wedge can creep and/or the resilient member can wear and lesson the amount of preload, which can cause stator bars to loosen. In one testing method, a known force is applied to the stator wedge, the displacement of the stator wedge is measured, and the relationship between the force and displacement may be used to determine the health of the stator wedge and/or need for repair or replacement.